Non-woven cover sheets are used in the manufacture of disposable diapers in order to cover the absorbent pads of cellular material.
These cover sheets must not contain any holes through which the cellular material might fall. They must also not contain thickened areas which interfere with the rapid incorporation of the cover sheets into the diaper during manufacture. Also, foreign matter on the cover sheet such as flies or dirt are obviously undesirable since it would be disturbing to customers.
During the manufacture of diapers, the cover sheet is supplied to the diaper making machine in the form of a continuous web. In the past, the cover sheet web has been monitored by a line camera with a lens. Such cameras are susceptible to soiling; they are also difficult to align and must be mounted at a significant distance from the web.
The main object of the present invention is to provide an improved method and apparatus for monitoring cover sheet webs used in the manufacture of diapers.
A more specific object of the invention is to provide an apparatus and method for monitoring cover sheet webs used in the manufacture of diapers which overcome the abovementioned deficiencies of the known monitoring systems.
A further object of the invention is to provide a monitoring system of the type described wherein the resolution (number of available sensor points for a given width of the web) is greater than with current monitoring systems.